Surgical fasteners are used to attach two or more tissue members to one another. A typical fastener consists of a relatively thin flexible filament having a relatively rigid, bar-like head on at least one end thereof, wherein the bar-like head normally resides perpendicular to the adjoining length of filament during use. In U.S. Pat. No. 4,669,473, issued on Jun. 2, 1987 to Richards et al., there is shown such a surgical fastener, generally referred to as a "T-bar" type of fastener. The fastener is deployed, for example, by anchoring the fastener's bar-like head in a human bone by means of a special tool, with the filament threaded through the tissues to be joined. The several tissue members may then be captivated on the filament between the fastener head and the end of the filament by tying a knot on the free end of the filament. In U.S. Pat. No. 4,669,473 there is shown a filament which has a plurality of ribs formed along its filament of conical shape, with the large end of each cone closer to the head. An associated washer is slid over the free end of the filament in the direction of the head end and brought to bear against the outermost tissue to be joined. The washer cannot move backwards away from the head end because of the conical nature of the ribs. A related concept is shown in U.S. Pat. No. 4,532,926, issued on Aug. 6, 1985 to O'Holla. Such an arrangement has proven to be costly and disadvantageous in that the body of the filament is required to be specially formed with conical elements. Further, since it may be desired to provide a certain degree of tension between the tissue members or the tissue members and bone, the stepped arrangement provided by the ribbed filament affords only a rudimentary degree of tensioning in predefined incremental amounts. Additionally, slight loosening may occur when the washer is set by the appropriate tool, since there is a tendency for the washer to slip backward to the next outboard conical rib when the washer is set.
Another form of tissue fastener arrangement is shown in European Patent Application Publication No. 0,129,442, published On Dec. 27, 1984, in which a staple type fastener has its legs brought through a bar member and wherein the legs are subsequently permanently deformed or coined to form a bulged out portion within the bar member, not unlike a "pop" rivet. Such a construction requires that metal or other material be used which has no memory, i.e., which can be deformed and which thereafter will not return to its former position. This requirement limits the use of such a construction to special materials which will retain this deformation when a special "setting" tool is removed after the staple is in place. Most materials used in fasteners which are intended to be absorbed by the human body would therefore not be capable of use in this type of staple.